1. Field of Use
The present invention relates to monitoring the operation of computer systems and, more particularly, to apparatus and methods for independently capturing events in a system and subsequently correlating those events in time.
2. Prior Art
A recurring problem in monitoring the performance and operation of computers system, for example, on a computer system bus during operation, is that of the ability of the user of a monitoring apparatus to capture conditions occurring independently in the system and to subsequently relate those conditions to one another and in time. For example, the user of a monitoring apparatus of the prior art generally has the ability to capture all of the events occurring within a given time after initiation of the monitoring process, be not the ability to independently and selectively capture information related to events that might occur at any time in system operation, and to later correlate those events. That is, the monitoring apparatus of the prior art operates in much the same manner as a tape recorder, turn it on and it records everything that happen until it runs out of tape. Unless, therefore, the storage capabilities of a monitoring device are impracticably large, the user has difficulty in capturing events that may occur only at infrequent intervals or only long after the monitoring process has started and may not, in fact, capture the events of interest because the monitoring device's data recording apparatus becomes saturated, or filled, with data. This is particularly true in the case of events which are either intermittent, such as certain types of failures, or which happen only infrequently in the normal operation of a system. In order to overcome this limitation, it is necessary to capture such events independently of one another. This, however, leads to another problem and related problem of system monitors of the prior art in that it is usually difficult to determine the time at which such independent events occurred, and to correlate those events with one another in time.